Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$165.46	11.171%	$183.9435	$183.94	$183.95	$183.90
Purchase #2	$38.53	8.570%	$41.832	$41.83	$41.85	$41.80
Purchase #3	$118.29	10.314%	$130.4904	$130.49	$130.50	$130.50
Purchase #4	$6.56	8.616%	$7.1252	$7.13	$7.15	$7.10
Purchase #5	$109.32	12.553%	$123.0429	$123.04	$123.05	$123.00
Purchase #6	$222.93	12.694%	$251.2287	$251.23	$251.25	$251.20
Purchase #7	$25.47	9.563%	$27.9057	$27.91	$27.90	$27.90
7 purchase totals =	$686.56		$765.5684	$765.57	$765.65	$765.40